Investigating the role of water on CO2-Utica Shale interactions for carbon storage and shale gas extraction activities – Evidence for pore scale alterations
In this work, we probed the physical and chemical alteration of the carbonate-rich Utica Shale following CO 2 exposure when thin films of water were present at the shale surface. All reaction conditions were examined at 40 °C and CO 2 pressures up to 10.3 MPa for 14 days. CO 2 dissolution in the water layer at 2342 cm -1 and carbonate dissolution and precipitation at 1424, 874, and 712 cm -1 were discerned with in-situ Fourier Transform infrared spectroscopy (FT-IR). Significant etching and pitting from exposure to CO 2 and water were observed with feature relocation scanning electron microscopy (SEM). Application of the density function theory (DFT) for pore size analysis showed that micropores between approximately 0.9 and 2 nm disappeared while the mesopore volume increased after dissolution of carbonate. These results may provide new insights that carbonate rich shales such as the Utica may have a greater potential for alterations of pore space due to the reactivity of CO 2 which may affect 1) how CO 2 storage in shale formations plays a role in Carbon Capture and Storage (CCS) activities, 2) if CO 2 can be utilized as a potential fracturing agent, and 3) whether CO 2 is an effective fluid for enhanced hydrocarbon extraction.